regulator: as3711: Fix the logic in as3711_sel_check

Below equation means the "voltage" is the "smallest" voltage within specific
range.

ret = DIV_ROUND_UP(min - bottom) / step;
voltage = ret * step + bottom;

If we do try 1 down when (voltage > max), new voltage is then less than min
voltage. Which means the new voltage is not in the requested voltage range.

This patch also includes below cleanups:
- Use DIV_ROUND_UP
- rename variable 'ret' to 'sel' for better readability because as3711_sel_check
  returns the selector.
Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

drivers/regulator/as3711-regulator.c

@@ -93,24 +93,17 @@ static int as3711_bound_check(struct regulator_dev *rdev,
 
 static int as3711_sel_check(int min, int max, int bottom, int step)
 {
-	int ret, voltage;
+	int sel, voltage;
 
 	/* Round up min, when dividing: keeps us within the range */
-	ret = (min - bottom + step - 1) / step;
-	voltage = ret * step + bottom;
+	sel = DIV_ROUND_UP(min - bottom, step);
+	voltage = sel * step + bottom;
 	pr_debug("%s(): select %d..%d in %d+N*%d: %d\n", __func__,
-	       min, max, bottom, step, ret);
-	if (voltage > max) {
-		/*
-		 * Try 1 down. It will take us below min, but as long we stay
-		 * above bottom, we're fine.
-		 */
-		ret--;
-		voltage = ret * step + bottom;
-		if (voltage < bottom)
-			return -EINVAL;
-	}
-	return ret;
+	       min, max, bottom, step, sel);
+	if (voltage > max)
+		return -EINVAL;
+
+	return sel;
 }
 
 static int as3711_map_voltage_sd(struct regulator_dev *rdev,